This disclosure relates generally to a power supply technology, and more particularly to a pulsed power system and control method thereof.
Pulsed power is unique technology that can compress energy into a short but intense burst to create extreme conditions without the demand for a very large energetic power source. The pulsed power has been widely utilized in many industrial areas, such as magnetic resonance imaging (MRI).
In general, MRI examinations are based on the interactions among a primary magnetic field, a radiofrequency (RF) magnetic field and time varying magnetic gradient fields with gyromagnetic material having nuclear spins within a subject of interest, such as a patient. The magnetic fields used to generate images in MRI systems include a highly uniform, static magnetic field that is produced by a primary field magnet. A series of gradient fields are produced by a set of gradient coils located around the subject. The gradient fields encode positions of individual plane or volume elements (pixels or voxels) in two or three dimensions. An RF coil is employed to produce an RF magnetic field. This RF magnetic field perturbs the spins of some of the gyromagnetic nuclei from their equilibrium directions, causing the spins to precess around the axis of their equilibrium magnetization. Certain gyromagnetic materials, such as hydrogen nuclei in water molecules, have characteristic behaviors in response to external magnetic fields. The precession of spins of these nuclei can be influenced by manipulation of the fields to produce RF signals that can be detected, processed, and used to reconstruct a useful image.
In a MRI system, the gradient drivers are configured to excite gradient coils located around an object, for example a patient, to generate magnetic field gradients along X-axes direction, Y-axes direction and Z-axes direction. The time-varying magnetic gradient fields are driven by pulsed sequences of current having a large dynamic range. A gradient driver generally includes an array of semiconductors connected in series and/or parallel which may be stacked to drive a higher amplitude pulse sequence. However, typical configurations of gradient drivers do not have both high switching frequency and low switching loss.